Electric cartridge fuses having blade contacts



SWAIN ELECTRIC CARTRIDGE FUSES HAVING BLADE CONTACTS Filed 6. 1968 VFW- gm INVENTOR; KENNETH W. SWAIN United States Patent 3,529,27 ELECTRIC CARTRIDGE FUSES HAVING BLADE CONTACTS Kenneth W. Swain, North Hampton, N.H., assignor to The Chase-Shawmut Company, N ewburyport, Mass. Filed Aug. 6, 1968, Ser. No. 750,569 Int. Cl. H01h 85/16 US. Cl. 337-236 1 Claim ABSTRACT OF THE DISCLOSURE BACKGROUND OF INVENTION The problem of firmly maintaining the constituent parts of a knife-blade type fuse in their positions is one of the most important problems in the design of electric knifeblade type fuses. It has found many solutions, but still calls for improved solutions. The present invention is such an improved solution to the aforementioned problem.

SUMMARY OF INVENTION Electric fuses embodying this invention include a tubular casing of insulating material which is filled with a pulverulent arc-quenching filler. A fusible element is embedded in said arc-quenching filler. A pair of terminal caps closes the axially outer ends of said casing. The end surface of each of said pair of caps defines a slot extending across the center of said end surface. Fuses embodying this invention further include a pair of knife-bladecontacts conductively interconnected by said fusible element of which each projects transversely through said slot in said end surface of each of said pair of caps. The longitudinal edges of each of said pair of knife-bladecontacts have a pair of transverse incisions adjacent the axially inner ends thereof. Fuses embodying this invention further include a pair of washers each arranged between one of the rims of said casing and said end surface of one of said pair of caps. Each of said pair of washers defines an opening for the passage of one of said axially inner ends of said pair of knife-blade-contacts. Said opening of each of said pair of washers forms an edge projecting into said pair of transverse incisions of one of said pair of knife-blade-contacts and thereby precluding movement of said pair of knife-blade-contacts in a direction longitudinally thereof relative to said pair of washers. Said pair of washers has projections extending in a direction longitudinally of said casing forming abutments for locating each of said pair of washers during assembly operations relative to said casing.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is an isometric view of the constituent parts of one end of a fuse embodying the present invention;

FIG. 2 is a side elevation of the fuse shown in FIG. 1 some of the parts being broken away to expose to view the interior of the structure;

FIG. 3 is a top plan View of some of the parts of the structure of FIGS. 1 and 2 in a relatively early stage of assembly, this figure being drawn on a larger scale than FIGS. 1 and 2;

FIG. 4 shows the same parts as FIG. 3 in the same fashion as FIG. 3, however, in a more advanced state of assembly; and

3,529,271 Patented Sept. 15, 1970 FIG. 5 shows in part in section and in part in side elevation some of the parts shown in FIGS. 3 and 4.

DESCRIPTION OF PREFERRED EMBODIMENT Referring now to the drawings, number 1 has been applied to indicate a tubular casing of insulating material as, for instance, vulcanized fiber. Casing 1 is filled with a pulverulent arc-quenching filler 2, e.g. gypsum powder. A fusible element 3 in form of a multiperforated metal ribbon is embedded in arc-quenching filler 2. The axially outer ends of casing 1 are closed by a pair of terminal caps 4. The end surface 4a of each of said pair of caps defines a slot 4b extending across the center of said end surface. The structure further includes a pair of knife-blade-contacts 5 each projecting through said slot 411 in said surface 4a of each of said pair of caps 4. The axially inner ends of knife-blade-contacts 5 are conductively interconnected by fusible element 3. To this end the axially outer ends of fusible element 3 may be spotwelded to the axially inner ends of knife-blade-contacts 5 by spot welds (not shown). The longitudinal edges 5a of each of said pair of knife-blade-contacts 5 have a pair of transverse incisions 5b adjacent the axially inner ends thereof. A pair of washers 6a is arranged between the rims 1a of easing 1 and said end surface 411 of each of said pair of caps 4. Each of said pair of washers 6 defines an opening 6a for the passage of one of said pair of knife-bladecontacts 5. The axially inner ends of knife-blade-contacts 5 project through openings 6a in washers 6 and through slots 4b in caps 4. The openings 6a in washers 6 form edges 6b projecting into incisions 5b of edges 5a of knife-blade-contacts 5, thereby precluding movement of knife-blade-contacts 5 in a direction longitudinally thereof relative to Washers 6. As shown in FIGS. 1, 3 and 4 edges 6b are curvilinear and have progressively decreasing radii of curvature. As shown in FIG. 3 the portions of edges 61) of washers 6 adjacent the edges 5a of knifeblade-contacts 5 have a larger radius of curvature than the portions of edges 6b of washers 6 remote from the edges 5a of knife-blade-contact 5. The spacing between the first mentioned portions of edges 6b, i.e. the portions having a relatively large radius of curvature, exceeds the width of knife-blade-contacts 5, i.e. the distance between the longitudinal edges 5a thereof. As a result, knife-bladecontacts 5 may readily be threaded through openings 6a. Thereupon the respective washer 6 is pivoted degrees in counterclockwise direction as seen in FIG. 3 to the position thereof shown in FIG. 4. In that position the portions of edges 6b of washers 6 having a relatively small radius of curvature and having a relatively small spacing from each other are situated immediately adjacent the longitudinal edges 5a of knife-b1ade-contacts 5 and project into the incisions 5b of the latter. Thus washers 6 and knife-blade-contacts 5 jointly form bayonet-type fastener means precluding any movement of either of knife-blade-contacts 5 in a direction longitudinally thereof relative to washers 6. Each of washers 6 has three projections 6c arranged in a circular pattern whose outer diameter is substantially equal to the inner diameter of casing 1. Projections 6c are angularly displaced degrees. Projections 60 extend in a direction longitudinally of casing 1 and form abutments locating washers 6 relative to casing 1 during assembly operation. In other words, projections 60 are arranged along a plurality of angularly displaced straight lines. Each projections 60 is formed by a portion of one of the washer 6 bent 90 degrees out of the general plane of the respective washer. Such bending can be conveniently achieved by a forming tool which pierces the washers 6, thereby forming eyelet-like cylindrical projections 60 on the surfaces of washers 6 intended to become the axially inner surfaces thereof. The clearance between the inner surface of casing 1 and tubular projections 60 is relatively small, as indicated in FIGS. 3 and 4, and thus the inner surface of easing 1 guides washers 6 when the latter are pivoted from the position thereof shown in FIG. 3 to the position thereof shown in FIG. 4. When this pivotal movement has been completed the ends of edges 6b having relatively small radii of curvature and having a relatively small spacing from each other frictionally engage the longitudinal edges a of knife-blade-contacts 5 at the points thereof where the incisions 5b are located, thus imparting a high degree of dimensional stability to the fuse structure.

FIG. 1 shows but one end of a fuse embodying this invention, but the other end thereof is substantially the same as the end shown in FIG. 1, and thus does not call for an isometric representation thereof.

It will be understood that I have illustrated and described a preferred embodiment of my invention, and that various alterations may be made in the details thereof without departing from the spirit and the scope of the invention as defined in the appended claim.

I claim as my invention:

1. An electric cartridge fuse including:

(a) a tubular casing of insulating material;

(b) a pulverulent arc-quenching filler inside of said casing; 7

(c) a fusible element embedded in said arc-quenching filler;

(d) a pair of terminal caps closing the axially outer ends of said casing, the end surface of each of said pair of caps defining a slot extending across the center of said end surface;

(e) a pair of knife-blade-contacts conductively interconnected by said fusible element each projecting transversely through said slots in said end surface of each of said pair of caps, the longitudinal edges of each of said pair of knife-blade-contacts having a pair of transverse incisions adjacent the axially inner end of each of said pair of knife-blade-contacts;

(f) a pair of washers each engaged on one side thereof by one of the rims of said casing and on the other side thereof by said end surface of one of said pair of caps, each of said pair of washers defining an opening for the passage of said axially inner end of one of said pair of knife-blade-contacts, said opening of each of said pair of washers forming curvilinear edges having progressively decreasing radii of curvature arranged to project progressively into said pair of transverse incisions of one of said pair of knife-blade-contacts upon relative rotation of said pair of knife-blade-contacts and said pair of washers about the axis of said casing and thereby precluding movement of said pair of knife-blade-contacts in a direction longitudinally thereof relative to said pair of washers, and each of said pair of washers having a plurality of projections formed by portions of said pair of washers bent substantially degrees out of the general plane thereof, extending in a di rection longitudinally of said casing and arranged in a circular pattern having an outer diameter equal to the inner diameter of said casing, said projections forming abutments engaging the inner wall of said casing for locating each of said pair of washers relative to said casing during assembly operations.

References Cited UNITED STATES PATENTS 3,020,372 2/1962 Kozacka 337164 2,430,041 11/1947 Berthel 337248 2,168,791 8/1939 Carney 337231 XR 1,656,121 1/1928 La Mar 337253 XR 1,299,132 4/1919 Conant 337253 BERNARD A. GILHEANY, Primary Examiner D. M. MORGAN, Assistant Examiner US. Cl. X.R. 337248, 254 

